Coated stent with geometry determinated functionality and method of making the same

ABSTRACT

The present invention, in an exemplary embodiment, provides a stent, which combines many of the excellent characteristics of both silicone and metal stents while eliminating the undesirable ones. In particular, a principal objective in accordance with the present invention is to provide a family of stents where the relative hardness/softness of regions of the stent can differ from other regions of the stent to provide additional patient comfort and resistance to compression forces. Exemplary embodiments provide a stent that is coated in a manner that limits the amount of coating surface area that is in direct contact with the target lumen. In particular, a covered stent is provided that is coated internally such that the outer scaffolding surface of the stent is raised from the outer surface of the coating. To this end, cilia function is only partially limited and mucociliary clearance is not significantly affected. Moreover, the coating itself has anti-adherent properties such that bacteria, fungi or other microbials cannot colonize the cover in particular and the stent generally.

PRIORITY CLAIM

[0001] This patent application is a continuation in part of and claimsthe benefit of priority under 35 U.S.C. § 120 to co-pending U.S.Nonprovisional application Ser. No. 10/288,615, filed Nov. 5, 2002,which is incorporated in its entirety by this reference.

FIELD OF INVENTION

[0002] The present invention relates generally to medical devicesdirected to the prevention of luminal occlusion, and more particularlyto stents and methods for making and utilizing these stents in thetreatment of both benign and malignant conditions wherein thefunctionality of the stents is determined by geometrical variability ofthe scaffolding and concomitant interstices.

BACKGROUND OF THE INVENTION

[0003] Stents are devices that are inserted into a vessel or passage tokeep the lumen open and prevent closure due to a stricture, externalcompression, or internal obstruction. In particular, stents are commonlyused to keep blood vessels open in the coronary arteries and they arefrequently inserted into the ureters to maintain drainage from thekidneys, the bile duct for pancreatic cancer or cholangiocarcinoma orthe esophagus for strictures or cancer. Vascular as well as not vascularstenting has evolved significantly; unfortunately there remainsignificant limitations with respect to the technology for producingstents suitable to various portions of a patient's anatomy.

[0004] Historically, in order to provide a stent with varyingcharacteristics, the stent had to be manufactured from multiplematerials, at least one for each characteristic desired. As a result,many of these stents are woven from two or more metals having differingshape-memories for example. Unfortunately, braided stents are vulnerableto premature obsolescence. Moreover, providing multiple material typesin a single stent may lead to inconsistent characteristics along thesurface area of the stent. This is particularly undesirable when thestent is to be placed in vascular or nonvascular lumens that have beenoccluded for one reason or another. The stent needs to be stiffer insome regions while more flexible in others.

[0005] Additionally, medical device companies have identified the needto cover stents at least partially to prevent the epithelialization ofthe scaffolding. Most covered stents however have an elastomeric coverthat is subject to bunching particularly about stenotic tissue. This canlead to additional tissue granulation. Alternatively, the stents are dipcoated which can lead to uneven coating as well as inconsistency instent performance from batch to batch.

[0006] Additionally the ends of the stent tend to be exposed in order toencourage granulation tissue formation, which helps to anchor the stentin place. With metal stents, the direct metal to tissue contactaccelerates tissue granulation and galvanic current generation is alsoan undesirable byproduct. Such direct current can have indirect effectson tissue granulation and direct effects on fluid flow dynamics.

[0007] Moreover, since many medical device companies have chosen to usepoorly adapted cardiovascular stents for Pulmonary, GI and PeripheralVascular indications, many of the anatomical differences in the lumensare not accounted for in stent design. For example, the pulsation of thecardiovascular lumen and the concomitant radial force requirements of acardiovascular stent differ substantially from that of a tightlyconstricted lumen such as the trachea during repeated coughing. When astent developed for the former is indicated for the latter, the stenttends to fail under the extreme conditions and lose its elasticity andtherefore its ability of ensure airway patency. Non-vascular lumens alsotend to have ciliated epithelia so as to facilitate clearance of fluidsand particulates. As a general principal, coated stents were notspecifically designed for ciliated lumen in that the external coatingdamages the cilia and prevents the body's natural clearing function.Moreover, the coating itself is usually made of a predominatelyhydrophilic polymer, which can lead to mucous formation and/or fluidstagnation. Stagnation of fluids or material passing through the lumencan lead to additional complications such as in stent restenosis orbacterial infections.

[0008] Therefore, there remains an existing need for a therapeutic stentthat can have varying characteristics along its surface area while beingstamped, not braded, from a single base material. Moreover, there is aneed for such a therapeutic stent where the relative hardness, softness,flexibility, stiffness and radial force can be modified as a function ofgeometric considerations rather than material considerations. Inparticular, there is a need for a stent that is divided into zones so asto allow the stent to have predetermined characteristics in one zone andcould conceivably have drastically different characteristics in anadjacent zone so as to allow for stents that can be tailored toanatomical lumens in general and the particular lumen topography of aspecific patient in particular. An additional need remains for a stentthat is coated in a manner that limits the amount of coating surfacearea that is in direct contact with the target lumen. In particular,there is a need for a covered stent that is preferably coveredinternally such that the outer scaffolding surface of the stent israised from the outer surface of the coating. To this end, ciliafunction is only partially limited and mucociliary clearance is notsignificantly affected. A need also remains for a coating that itselfhas anti-adherent properties or is complexed with an anti-adherent suchthat bacteria, fungi or other microbials cannot colonize the cover inparticular and the stent generally.

SUMMARY OF EXEMPLARY EMBODIMENTS

[0009] It is a principal purpose of the present invention to provide astent, in accordance with an exemplary embodiment of the presentinvention, which combines many of the excellent characteristics of bothsilicone and metal stents while eliminating the undesirable ones. Inparticular, it is an objective of a preferred embodiment in accordancewith the present invention to provide a stent that is easily installed,yet in alternative embodiments, removable. Moreover the stent inaccordance with this embodiment of the present invention would not causematerial infections and may be capable of reducing infection. Therefore,a principal objective of a preferred embodiment in accordance with thepresent invention is to provide a prosthesis that is suitable for bothpermanent and temporary use while being easy to insert, reposition andremove.

[0010] A principal objective of a preferred embodiment of the presentinvention is to provide a stent that may be stamped from preferably asingle material that is capable of maintaining its axial working lengthwhen radially compressed. To this end, the stent does not have a seamthat could aggravate luminal tissue. In particular, a stent inaccordance with the present invention is formed using a tool that moldsthe stents outer contour as well as its interstices.

[0011] It is yet another objective of an exemplary embodiment of thepresent invention to provide a stent that can be indicated for thetreatment of benign and malignant disease and improve the way clinicianstreat malignant obstructions.

[0012] Still another objective of the present invention is to provide astent and method for installing the stent that is economical andsuitable for routine purposes. Moreover, the stent will have minimalmigration, cause minimal tissue granulation, will not foreshorten afterdeployment and mucociliary clearance will not be problematic.

[0013] Yet another objective of an exemplary embodiment in accordancewith the present invention is to provide a prosthesis that will havesuperior internal to external diameter ratio, superior radial force withdynamic expansion, while being suitable for use in pediatric and adultpatients with malignant and benign disease.

[0014] A principal objective of an exemplary stent in accordance withthe present invention is to provide a family of stents where therelative hardness/softness of regions of the stent can differ from otherregions of the stent to provide additional patient comfort andresistance to radial forces.

[0015] An additional objective in accordance with an exemplaryembodiment is to provide a family of stents with novel intersticeconfigurations that facilitate flexibility, durability and/or properinstallation.

[0016] Still another objective of a preferred embodiment of the presentinvention is to provide a self-expanding stent having the above benefitsthat also defines a plurality of apertures at the termini of the stentfor, inter alia, removal of the stent.

[0017] An additional objective in accordance with a preferred embodimentof the present invention is to provide a prosthesis that minimizes ciliadestruction at the site of implantation. In the furtherance of this andother objectives, the preferred prosthesis is coated internally with apolyurethane such that the surfaces of the struts that come into contactwith the lumen of the patient are elevated above the surface of thecoating such that the cilia can move to allow for free fluid action ofciliated epithelium.

[0018] Further objectives, features and advantages of the invention willbe apparent from the following detailed description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

[0019]FIG. 1 shows a polarization microscopic image of a plurality ofzones of a stent in accordance with a preferred embodiment of thepresent invention.

[0020]FIG. 2 shows an alternative perspective view of the polarizationmicroscopic image of FIG. 1.

[0021]FIG. 3 shows an enlarged perspective view of the interstices of anexemplary zone as shown in FIG. 1.

DETAILED DESCRIPTION OF AN EMBODIMENT

[0022] A preferred embodiment of the stent, in accordance with thepresent invention, provides a stent that prevents epithelialization ofthe stent and is not subject to premature elongation and foreshorteningbut is capable of engaging the desired implantation location. The stentalso retains its axial length while undergoing radial compression.

[0023] The stent is preferably formed from a composite material selectedfrom the group consisting essentially of Ni, C, Co, Cu, Cr, H, Fe, Nb,O, Ti and combinations thereof. The composite material is generallyformed into a compressed tube from which the stent is etched and isformed on a suitable shaping device to give the stent the desiredexternal geometry. Both the synthetic collar techniques and in vitrovaluation techniques show the remarkable ability of stents in accordancewith the present invention to convert acting force into deformation workabsorbed by the angled structure, which prevents excessive scaffoldingstress and premature material fatigue and accelerated obsolescence.

[0024] Though one skilled in the stent engineering art, once apprised ofthe present application, would be able to manufacture a stent consistentwith the present invention by other methods, a preferred method ofmanufacturing such stents follows. As stated above a composite materialis selected and a blank is formed there from. The blank is preferablylaser etched and the etch work is generally verified for accuracy usingvisual recording microscopy. Dimensional measurements are taken toensure strut thickness, segment angles, zone placement, etc. Moreover,the stent is preferably formed on a shaping tool that has substantiallythe desired contour of the external stent dimensions.

[0025] In the event the stent is to be shaped to the dimensions of aparticular lumen, optical photography and/or optical videography of thetarget lumen may be conducted prior to stent formation. The geometry ofcorresponding zones and connector regions of the stent then can beetched and formed in accordance with the requirements of that targetlumen. For example, if the stent were designed for the trachea, whichhas a substantially D shaped lumen and additionally the middle zonesneeded to be softer than the end zones, the stent could be designed tothose specifications. With specific reference being made to FIG. 1, itcan be seen that angles α, β, δ, ε and γ may be modified to providedifferent characteristics to different zones of the stent. Inparticular, if the topography of the trachea of a particular patient iscaptured optically and the appropriate dimension provided, a patientspecific prosthesis could be engineered. These techniques can be adaptedto other non-vascular lumen but is very well suited for vascularapplications where patient specific topography is a function of avariety of factors such as genetics, lifestyle, etc.

[0026] It should be pointed out that unlike the use of differing shapememory materials to change regions of a stent, stents in accordance withthe present invention can take on an infinite number of characteristiccombinations as zones and segments within a zone can be modified bychanging angles, segment lengths and segment thicknesses during theetching and forming stages of stent engineering or during post formationprocessing and polishing steps. Moreover, by modifying the geometry ofthe connectors between zones, additional functionality may be achieved.

[0027] Exemplary stents 10 in accordance with the present invention areshown in FIGS. 1-3 showing the preferred interstice geometry. Not shownare a wide variety of interstice geometries that are also acceptablealternatives to the preferred, namely, U, V, W, Z, S and X geometries toname a few.

[0028] The stent 10 also is formed of memory metal and preferably hasunique geometrical interstices that are laser etched therein. However,other conventional ways of forming interstices in unitary stents, thoughnot equivalent are contemplated, may be employed and would be within theskill set of one in the art.

[0029] It cannot be overemphasized, however, that this does not mean theknowledge that changes in the geometry of interstices affect stentfunctionality is currently known in the art. To the contrary, thepresent inventors discovered the interrelation between intersticegeometry, width, length and relative resistance to torsional stress andradial force. In fact, it can be said that the stent 10 hascircumferential bands extending perpendicularly with respect to theluminal device's longitudinal axis. These bands are referred togenerally as zones. A connector 50 connects these bands to one another;the connector 50 is an additional means for adjusting stentfunctionality. In particular, the connector 50 defines a substantially Ushaped member, but could define other geometries such as U, V, W, Z, Sand X to name a few. As shown specifically in FIG. 1, δ, ε and γ vary inshape and that the corresponding region of the stent differs infunction. It can also be seen from FIG. 1, at least one but preferably aplurality of eyelets φ that allow a physician to purse string the stentwith suture to facilitate removability. The eyelets are preferablybetween about 200 μm and 300 μm, however, the eyelets may be smaller orlarger to accommodate the need of the target site. The preferred eyeletsize is about 350 μm as the preferred suture type is 4-0. The medicalappliance may be pre-threaded with suture or the user may provide thesuture after implantation.

[0030] In a standard orientation, as shown particularly in FIG. 2, thesubstantially U-shape connector comprises preferably two leg members 52& 56 and a crossing member 54 that connects with and extendsperpendicularly at preferably 90° angles with respect to the leg members52 & 56. It must be noted that alternative angles may be providedwithout departing materially from the invention. The present inventorsdiscovered that if you modify the length of the crossing member 54and/or the leg members 52 & 56 and/or the angle γ at which the crossingmember 54 and the leg members 52 & 56 intersect, the relativehardness/softness, radial force and/or flexibility of the stent 10 couldbe modified. The angles γ can be modified at varying acute angles shortof 90° or varying obtuse angles greater than 90°. The incrementalchanges correspondingly change certain characteristics of the stent 10.As a result, different zones of the stent 10 can be given differentrigidities to improve patient comfort and for example, in airway stents,to facilitate luminal patency. Moreover, various anatomical lumens mayneed different degrees of stent rigidity. As a result, stents 10 inaccordance with the present invention can be manufactured to exactingspecifications to contour properly to various lumens in a patient'sanatomy, which may need varying levels of structural support from themedical appliance.

[0031] Referring now to FIG. 3, there is an enhanced capability providedby stents in accordance with the present invention. By adjusting thedistance between the connector 50 and the zones between which connector50 resides, the way in which the stent reacts to strain can be modified.By way of non-limiting example, if the connector 40 is oriented closerto one zone than to another zone, the stent will be less flexible and beable to withstand greater radial force. Alternatively, if the connectoris equidistant between zones, the stent will be more flexible and beable to withstand less radial force. Please note that these differencesare relative to a neutrally located connector 40. The behavior is afunction of distance and as a result varies along a continuum withrespect to the connector's orientation between the medium between zonesand the tip of each zone. Moreover, within by varying the number ofconnectors 40 that connect the zones to one another, functionality canbe impacted. In particular, the fewer the number of connectorsconnecting the zones the more torsional flexibility the stent will have.The converse will generally hold true with respect to a greater numberof connectors.

[0032] Connector 40, which serves a similar purpose as connector 50 alsohas a crossing member 44 that connects leg members 42 & 46 at apredetermined angle δ. As discussed above, since form follows functionfor stents prepared through this novel method, by changing the degreesof angles αβ,δ& γ, stent characteristics can be modified. Moreover, bychanging the leg lengths of all the previously discussed legs orindividual legs separately, additional stent characteristics can beobtained. The beauty of this system is that the desired characteristicscan be determined prior to forming the stent and by staying withincertain forming parameters, the stent can be formed, crimped, deliveredand deployed with confidence that the desired functionality with result.This is important in light of the fact that both vascular andnonvascular lumen have unique topography. As a result, methods anddevices in accordance with the present invention usher in the ability totailor prosthesis to anatomical tissue in general and particular patientanatomy in particular.

[0033] The U shaped connectors 40 & 50 have a crossing member and atleast two leg members, respectively. The present inventors discoveredthat if you increase/decrease the length of leg members and/orincrease/decrease the length of crossing members and/or vary the angleat which crossing members and leg members intersect, you affect thefunctionality of the stent. In particular, the shorter the length of theleg members, the less flexibility available in that portion of thestent. Taking particular note of FIG. 3, by way of example only, if youwant to decrease the amount of torsional flexibility of the stent 10,you would have to modify the connector 40 so that the legs 42 & 46 arelonger than shown and that the angle δ formed by legs 42 & 46 andcrossing member 44, respectively, is slightly greater than 90°.Alternatively, the length of the crossing member 44 can impact thefunctionality of the stent as well. The stent can be made more rigid byshortening crossing member 44 or the stent may be made more flexible bylengthening crossing member 44. It should be noted that the combinationof the changes of leg lengths, crossing member lengths, anglevariations, shapes and number of connectors provide the stent with theability to conform to specific lumens in the anatomy of a patient. Theresult is a form fitting medical prosthesis that may be tailored tospecific anatomical lumens in general and to the anatomical lumens of anindividual patient in particular.

[0034] In a preferred embodiment, the modification of intersticegeometries and manipulation of the U shaped connection member to achievevariable stent functionality is provided. The rigidity of the stentscaffolding or interstice matrix along with the torsionality of thestent itself is principally a function of these modifications. In anexemplary embodiment, the stents relative flexibility can be rated soft,medium or hard based on the degree of flex and torsionality. The lesstorsionality and flex in the stent the harder the stent is rated.

[0035] An exemplary stent in accordance with the present invention withrelatively great torsionality and radial flexibility would be ratedsoft. An exemplary soft rated stent comprises distance between U shapedconnectors of about 4.5 μm in the compressed state (i.e., contracted inthe 3 mm tube subject to laser etching). Moreover, the length of thecrossing member is preferably about 1.0 μm. The lengths of the legmembers are preferably about 1.5 μm long. Additionally the leg membersmay further comprise feet that attached to the remainder of the stentscaffolding. The feet can be adjusted from a standard length of about0.25 μm to further adjust the characteristics of the stent. There isadditionally a substantially rectangular member incorporated in the Ushaped connector with similar capacity for variability. The variabilityfactors and results of modifying the dimensions of the substantiallyrectangular members are similar to those evinced by leg lengthdimensional modifications.

[0036] By way of example, but not to be construed in any way aslimiting, the softness index or relative flexibility can be increase byincreasing the various lengths discussed above. For example, byincreasing the length of the legs and crossing members of the U shapedconnector, flexibility increases. However, with respect to the distancebetween U shaped members and distance between interstices in a preferredstent embodiment, there is an inverse correlation between length andsoftness. This relative softness/hardness indexing as a corollary ofinterstice dimensions is a novel aspect of preferred embodiment of thepresent invention. As a practical rule of thumb, longer leg lengthscoupled with acute angles provide for greater flexibility. Conversely,shorter leg lengths and more obtuse angles provide more rigidity. By wayof non-limiting example, a U shaped connector with short legs deviatingfrom the crossing member at angles greater than 90°, will be extremelyrigid and resistant to torsional strain as compared to a U shapedconnector with longer legs diverging from the crossing member at anglesless than 90°.

[0037] In addition to the length and spacing differences, theinterstices themselves may define various shapes that by their verynature afford novel functionality to the stent. The changes offunctionality, however, are more a function of the dimensionaldifferences of the various shapes rather than a function of the shapesthemselves. Therefore, it is important to keep in mind that thedimensional differences discussed in the previous paragraph aredeterminative of the functionality accorded the stent by the varyinginterstice geometries. It is for this reason that one of ordinary skillin the art, after being apprised of the present invention, would be ableto conceive of a number of interstice geometries to satisfy certainfunctionality criteria by keeping certain dimensional parametersconstant.

[0038] FIGS. 1-3 also show the coating provided in select embodiments inaccordance with the present invention. The coating 100 preferablycomprises a stable polymeric material such as polyurethane that can bedeposited on a stent to form a thin film. The film preferably formslayers when annealed to the stent such that the hydrophobic moietieswithin the polymer are predominately oriented outward and thehydrophilic moieties are predominately oriented inward. It should benoted that depending on the characteristics desired by the user, therelative hydroaffinity may be altered. For example, in the event theimplant was placed with the intention of collecting mucous in therespiratory system, the coating 100 would more suitably have apredominately hydrophilic outer surface. Moreover, by manipulating thehydroaffinity of the coating 100, the physiochemical parameters such assurface-free energy, charge density provide a substantial barrier tobiofilm formation in general and ligand-binding events mediated bymicrobial adhesions and extracellular polymers. However, additionalanti-adherents know in the art may be applied to provide lubricity aswell as an additional barrier for microbials. For example, a preferredcoating 100 in accordance with the present invention would behydrophilic and hydroscope to ensure the surface would always be wetwhich prevents mucostasis as well as microbial adherence.

[0039] Regardless of desired coating surface characteristics, preferredstents in accordance with the present invention are coated from theinterior of the stent lumen such that the stent scaffolding is raisedabout between 1 Å to 10⁶ Å above the surface of the coating 100 as shownin FIG. 3 as indicia 200. One of the principal functions of sucharchitecture is to facilitate cilia action by allowing cilia movementbetween stent struts.

[0040] The stent is preferably coated in a multi-step process, whichcomprises providing a stent and initially spraying the stent with apolymeric material to coat the struts. Though the steps may be reversedit is preferable to follow the spraying step with the interior coatingstep. In particular, the stent is placed into a hollow mold to retainthe stent shape as the internal diameter of the stent is coated with thepolymeric material to form a non-porous coating 100. The coating 100 canbe provided in sheets or additional spray applications, however, thepreferred embodiment is the sheets. Sheets are generally preferred tofacilitate the proper orientation of the polymer side chains to ensurethat the desired moiety (e.g., hydrophilic and/or hydrophobic) is facingthe lumen. Once the layer of polymer is introduced into the innerdiameter of the stent, a balloon or other device in which temperaturecan be regulated is implanted to sandwich the layer of polymer betweenthe stent inner diameter and the balloon. The balloon is expanded andheated to a temperature of about between 200° and 400° F. to anneal thepolymer to the stent. Preferred polymers such as various designerpolyurethanes (e.g., Cronoflex® manufactured by CardiotechInternational) are suitable for such applications but other polymers areacceptable.

[0041] The present invention may be embodied in other specific formswithout departing from its spirit or essential characteristics. Thedescribed embodiments are to be considered in all respects only asillustrative, and not restrictive. The scope of the invention is,therefore, indicated by the appended claims, rather than by theforegoing description. All changes, which come within the meaning andrange of equivalency of the claims, are to be embraced within theirscope.

What is claimed is:
 1. A medical appliance for placement within aportion of the anatomy of a patient, the appliance comprising: ascaffolding, the scaffolding configured to define a substantiallycylindrical member having a distal end and a proximal end and extendinglongitudinally there between, forming a lumen there through, along thelongitudinal extension of the appliance the scaffolding having aninterior and an exterior surface comprising struts with geometricalpatterns formed by angles, wherein the angles determine the relativeflexibility of the medical appliance such that the appliance conforms tothe topography of a target lumen and when pressure is exerted alongvarying points of the longitudinal extension of the appliance, theappliance does not undesirably foreshorten or elongate.
 2. The medicalappliance of claim 2, wherein the scaffolding further comprises acoating coupled with the scaffolding such that both the struts and thearea between the struts are coated, the coating of sufficient thicknessto prevent the medical appliance from becoming epithelialized wheninstalled in the desired portion of the patient's anatomy.
 3. Themedical appliance of claim 2, wherein the coating is substantiallyhydrophobic.
 4. The medical appliance of claim 2, wherein the coating issubstantially hydrophilic.
 5. The medical appliance of claim 3, whereinthe coating is hydroscopic.
 6. The medical appliance of claim 4, whereinthe coating is substantially hydroscopic.
 7. The medical appliance ofclaim 1, wherein at least one strut defines an aperture there through.8. The medical appliance of claim 7, wherein the at least one aperturedefines an eyelet of sufficient diameter to receive suture.
 9. Themedical appliance of claim 8, wherein the eyelet diameter is at least300 μm.
 10. The medical appliance of claim 2, wherein the coating doesnot inhibit flexing or radial expansion of the medical appliance. 11.The medical appliance of claim 10, wherein the coating is coupled withthe medical appliance from the interior surface of the scaffoldingoutward.
 12. The medical appliance of claim 11, wherein the coating iscoupled with the medical appliance from the exterior surface of thescaffolding inward.
 13. The medical appliance of claim 2, wherein thecoating is coupled with the medical appliance from the exterior surfaceof the scaffolding inward.
 14. The medical appliance of claim 13,wherein the coated struts on the exterior surface of the scaffolding areraised with respect to the coated region between the struts of themedical appliance.
 15. The medical appliance of claim 14, wherein thecoated strut is raised between 1 Å to 106 Å with respect to the coatedregion between the struts of the medical appliance.
 16. The medicalappliance of claim 14, wherein the relative extent to which the coatedstruts are raised with respect to the coated regions between the strutsis sufficient to allow cilia function at the cite of implantation. 17.The medical appliance of claim 1, wherein the dimensions of thescaffolding geometry determine torsionality of the medical appliance.18. The medical appliance of claim 1, wherein the scaffolding is formedof a memory capable alloy.
 19. The medical appliance of claim 18,wherein the scaffolding is electropolished.
 20. The medical appliance ofclaim 1, wherein along the longitudinal expanse of the scaffolding themedical appliance further comprise a plurality of flanges that defineapertures there through.
 21. The medical appliance of claim 1, furthercomprising a connector coupled with portions of the geometricalpatterns, the connector comprising a crossing member and a plurality ofleg members extending from the crossing member.
 22. The medicalappliance of claim 21, wherein the connector further comprises arectangular detent extending from a leg thereof.
 24. The medicalappliance of claim 21, wherein the length of the leg members and thedegree of the angle at which the legs extend from the crossing memberdetermines the relative flexibility of the medical appliance.
 25. Themedical appliance of claim 23, wherein the angle at which the legmembers extend from the crossing member is greater than 90°.
 26. Themedical appliance of claim 25, wherein the medical appliance isrelatively rigid.
 27. The medical appliance of claim 25, wherein theangle at which the leg members extend from the crossing member is 90° orless.
 28. The medical appliance of claim 26, wherein the medicalappliance is relatively flexible.
 29. The medical appliance of claim 1,further comprising an additional distal end wherein the medicalappliance forms a substantially Y-shape.
 30. The medical appliance ofclaim 29, wherein at least one strut defines an aperture there through.31. The medical appliance of claim 30, wherein the at least one aperturedefines an eyelet of sufficient diameter to receive suture.
 32. Themedical appliance of claim 31, wherein the eyelet diameter is at least300 μm.
 33. The medical appliance of claim 29, wherein along thelongitudinal extension of the appliance, the scaffolding formsgeometrical patterns.
 34. The medical appliance of claim 33, wherein thescaffolding further comprises a coating coupled with the scaffolding,the coating of sufficient thickness to prevent the medical appliancefrom becoming epithelialized when installed in the desired portion ofthe patient's anatomy.
 35. The medical appliance of claim 34, whereinthe dimensions of the scaffolding geometry determine torsionality of themedical appliance.
 36. The medical appliance of claim 35, wherein thescaffolding is formed of a memory capable alloy.
 37. The medicalappliance of claim 35, wherein the scaffolding is electropolished. 38.The medical appliance of claim 34, wherein near the distal and proximalends of the scaffolding the medical appliance further comprise aplurality of flanges that define apertures there through.
 39. Themedical appliance of claim 29, further comprising a connector membercoupled with portions of the geometrical patterns, the connectorcomprising a crossing member and a plurality of leg members extendingfrom the crossing member.
 40. The medical appliance of claim 38, whereinthe connector further comprises a rectangular detent extending from aleg thereof.
 41. The medical appliance of claim 39, wherein the lengthof the leg members or the degree of the angle at which the legs extendfrom the crossing member positively contributes to the relativeflexibility of the medical appliance.
 42. The medical appliance of claim41, wherein the angle at which the leg members extend from the crossingmember is greater than 90°.
 43. The medical appliance of claim 42,wherein the medical appliance is relatively rigid.
 44. The medicalappliance of claim 41, wherein the angle at which the leg members extendfro the crossing member is 90° or less.
 45. The medical appliance ofclaim 44, wherein the medical appliance is relatively flexible.
 46. Amethod of coating a medical appliance, comprising the steps of:providing a mold having an internal and an external diameter; providinga medical appliance comprising a scaffolding, the scaffolding configuredto define a substantially cylindrical member having a distal end and aproximal end and extending longitudinally there between, forming a lumenthere through, along the longitudinal extension of the appliance thescaffolding having an interior and an exterior surface with geometricalpatterns formed by angles, wherein the angles determine the relativeflexibility of the medical appliance such that the appliance conforms tothe topography of a target lumen and when pressure is exerted alongvarying points of the longitudinal extension of the appliance, theappliance does not undesirably foreshorten or elongate; inserting themedical appliance into the internal diameter of the mold; applying apolymer to the interior surface of the medical appliance; and annealingthe polymer to the stent by applying heat to the polymer.
 47. The methodof claim 46, further comprising the step of applying a polymer to theexterior surface of the medical appliance.
 48. The medical appliance ofclaim 46, further comprising an additional distal end wherein themedical appliance forms a substantially Y-shape.